De-skewed multi-die packages

ABSTRACT

A microelectronic package may have a plurality of terminals disposed at a face thereof which are configured for connection to at least one external component. e.g., a circuit panel. First and second microelectronic elements can be affixed with packaging structure therein. A first electrical connection can extend from a respective terminal of the package to a corresponding contact on the first microelectronic element, and a second electrical connection can extend from the respective terminal to a corresponding contact on the second microelectronic element, the first and second connections being configured such that a respective signal carried by the first and second connections in each group is subject to propagation delay of the same duration between the respective terminal and each of the corresponding contacts coupled thereto.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Application 61/506,889 filed Jul. 12, 2011, the disclosureof which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to microelectronic packages or assembliesand methods of making such assemblies, and to components useful in suchassemblies.

Semiconductor chips are commonly provided as individual, prepackagedunits. A standard chip has a flat, rectangular body with a large frontface having contacts connected to the internal circuitry of the chip.Each individual chip typically is mounted in a package which, in turn,is mounted on a circuit panel such as a printed circuit board and whichconnects the contacts of the chip to conductors of the circuit panel. Inmany conventional designs, the chip package occupies an area of thecircuit panel considerably larger than the area of the chip itself. Asused in this disclosure with reference to a flat chip having a frontface, the “area of the chip” should be understood as referring to thearea of the front face. In “flip chip” designs, the front face of thechip confronts the face of a package substrate, i.e., chip carrier andthe contacts on the chip are bonded directly to contacts of the chipcarrier by solder balls or other connecting elements. In turn, the chipcarrier can be bonded to a circuit panel through terminals overlying thefront face of the chip. The “flip chip” design provides a relativelycompact arrangement; each chip occupies an area of the circuit panelequal to or slightly larger than the area of the chip's front face, suchas disclosed, for example, in certain embodiments of commonly-assignedU.S. Pat. Nos. 5,148,265; 5,148,266; and 5,679,977, the disclosures ofwhich are incorporated herein by reference.

Certain innovative mounting techniques offer compactness approaching orequal to that of conventional flip-chip bonding. Packages which canaccommodate a single chip in an area of the circuit panel equal to orslightly larger than the area of the chip itself are commonly referredto as “chip-sized packages.”

Size is a significant consideration in any physical arrangement ofchips. The demand for more compact physical arrangements of chips hasbecome even more intense with the rapid progress of portable electronicdevices. Merely by way of example, devices commonly referred to as“smart phones” integrate the functions of a cellular telephone withpowerful data processors, memory and ancillary devices such as globalpositioning system receivers, electronic cameras, and local area networkconnections along with high-resolution displays and associated imageprocessing chips. Such devices can provide capabilities such as fullinternet connectivity, entertainment including full-resolution video,navigation, electronic banking and more, all in a pocket-size device.Complex portable devices require packing numerous chips into a smallspace. Moreover, some of the chips have many input and outputconnections, commonly referred to as “I/O's.” These I/O's must beinterconnected with the I/O's of other chips. The interconnectionsshould be short and should have low impedance to minimize signalpropagation delays. The components which form the interconnectionsshould not greatly increase the size of the assembly. Similar needsarise in other applications as, for example, in data servers such asthose used in internet search engines. For example, structures whichprovide numerous short, low-impedance interconnects between complexchips can increase the bandwidth of the search engine and reduce itspower consumption.

Packages and assemblies containing multiple chips are common forpackaging chips that contain memory storage arrays, particularly fordynamic random access memory chips (DRAMs) and flash memory chips. Eachpackage has many electrical connections for carrying signals, power andground between terminals, i.e., external connection points of thepackage, and the chips therein. The electrical connections can includedifferent kinds of conductors such as horizontal conductors, e.g.,traces, beam leads, etc., which extend in a horizontal directionrelative to a contact-bearing surface of a chip, vertical conductorssuch as vias, which extend in a vertical direction relative to thesurface of the chip, and wire bonds which extending in both horizontaland vertical directions relative to the surface of the chip.

The transmission of signals within packages to chips of multi-chippackages poses particular challenges, especially for signals common totwo or more chips in the package such as clock signals, and address andstrobe signals for memory chips. Within such multi-chip packages, thelengths of the connection paths between the terminals of the package andthe chips can vary. The different path lengths can cause the signals totake longer or shorter times to travel between the terminals and eachchip.

Travel time of a signal from one point to another is called “propagationdelay” and is a function of the conductor length, the conductor'sstructure, i.e., width, and other dielectric or conductive structure inclose proximity therewith.

Differences in the times at which a particular signal arrives atdifferent locations is called “skew”. Differences in the times at whichtwo different signals reach a particular location can also be called“skew”. The skew in the arrival times of a particular signal at two ormore locations is a result of both propagation delay and the times atwhich the particular signal starts to travel towards the locations. Skewmay or may not impact circuit performance. Skew often has little impacton performance when all signals in a synchronous group of signals areskewed together, in which case all signals needed for operation arrivetogether when needed. However, this is not the case when differentsignals of a group of synchronous signals needed for operation arrive atdifferent times. In this case the skew impacts performance because theoperation cannot be performed unless all needed signals have arrived.

FIG. 1 illustrates an example of signal skew and its potential impact onperformance. FIG. 1 is a graph illustrating transitions in signalsAddr0, Addr1, and Addr2 needed for operation by each of a plurality ofmemory chips, e.g., DRAM chips within a package or module. As depictedin FIG. 1, due to different propagation delays, the Addr signals arriveat the DRAM chips at different times. Thus, Addr0 transitions betweenlow and high signal levels (or between high and low signal levels)before Addr1 transitions between signal levels. Likewise, Addr1transitions between signal levels before Addr2 transitions betweensignal levels.

The problem with synchronous signals from the package arriving at thecontacts of a chip at different times is that this limits the speed orfrequency at which the chip can transmit or receive the signals. Tofunction properly, all synchronous signals required for an operationneed to have arrived before the operation can be performed. Aconsequence of synchronous signals arriving at different times is thatthe frequency used to clock the signals into the chip may have todecrease. FIG. 1 further illustrates two intervals based on differentarrival times of the signals involved. The first interval is set up time102 based on the interval between the latest arriving signal and thesampling clock transition labeled CK in FIG. 1. The second interval ishold time 104 which is based on the interval between the sampling clocktransition CK and the earliest arriving signal in the next successiveclock cycle of operation. The time at which the signals are latched intothe chip within the package is indicated by “CK”. For best performanceper a given clock frequency it is desirable to maximize both the setuptime and hold time.

In light of the background described above, further improvements can bemade to multi-chip packages and assemblies to address skew.

SUMMARY OF THE INVENTION

A microelectronic package according to an aspect of the inventionincludes packaging structure having a plurality of terminals disposed ata face thereof, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage. First and second microelectronic elements can be affixed withthe packaging structure. The package includes connections electricallycoupling the terminals of the package with the first and secondmicroelectronic elements. The connections can include groups ofconnections for carrying respective signals, each group including two ormore connections, e.g., a first connection extending from a respectiveterminal of the package to a corresponding contact on the firstmicroelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element. The first and second connections can beconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto.

In accordance with a particular aspect of the invention, a differencebetween the total electrical lengths of the connections in a respectivegroup of the connections can be not greater than 10 percent, even whendistances along straight lines between the terminal and the respectivecontacts coupled by such group of connections varies by greater than 10percent.

In accordance with an aspect of the invention, the matched delay mayresult at least partly from differences in a spacing of conductors inthe electrical connections relative to other conductive structure of thesubstrate.

In accordance with an aspect of the invention, a microelectronic packagemay further include a circuit panel having circuit contacts, wherein theterminals of the package are electrically connected to the circuitcontacts.

In accordance with a particular aspect of the invention, at least one ofthe signals may be a clock signal or a command signal.

In accordance with a particular aspect of the invention, the signals mayinclude a plurality of address signals and a sampling signal used tosample the address signals.

In accordance with a particular aspect of the invention, the signals mayfurther include a command strobe signal.

In accordance with a particular aspect of the invention, the sameduration of the propagation delay of the respective signal on the firstand second connections within each group may be within a tolerance often percent of the cycle time of that signal.

In accordance with a particular aspect of the invention, a thirdmicroelectronic element may be affixed with the packaging structure,wherein at least one of the groups of connections includes a thirdconnection electrically coupling the respective terminal to acorresponding contact of the third microelectronic element for carryingthe respective signal thereto, wherein the signal carried by the first,second and third connections is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto. In a particular example, a fourthmicroelectronic element may also affixed with the packaging structure,wherein at least one of the groups of connections includes a fourthconnection electrically coupling the respective terminal to acorresponding contact of the fourth microelectronic element for carryingthe respective signal thereto, wherein the signal carried by the first,second, third and fourth connections is subject to propagation delay ofthe same duration between the respective terminal and each of thecorresponding contacts coupled thereto.

In accordance with a particular aspect of the invention, the packagingstructure may have edges bounding the face, the face having a centralregion occupying a central portion thereof, and a second regionoccupying a portion of the face between the central portion and at leastone of the edges. The terminals may include first terminals exposed atthe central region and second terminals exposed at the second region,and the groups of connections couple the first terminals with thecorresponding contacts. In such case, in a particular example, themicroelectronic package may include further connections electricallycoupling the second terminals with contacts of the microelectronicelements.

In accordance with a particular aspect of the invention, the packagingstructure may include a substrate having first and second opposedsurfaces, the first surface facing away from the microelectronicelements and the second surface facing towards the microelectronicelements, at least first and second apertures extending between thefirst and second surfaces. In a particular example, the apertures mayhave long dimensions with lengths which extend along axes parallel toone another. The central region may be bounded at least partly by thefirst and second apertures, and the connections can include leads whichhave portions aligned with at least one of the first or secondapertures. In accordance with a particular aspect of the invention, theleads which have portions aligned with at least one of the apertures caninclude wire bonds. In a particular example thereof, the microelectronicpackage may further include third and fourth microelectronic elementseach affixed with the packaging structure, wherein at least one of thegroups of connections includes third and fourth connections electricallycoupling the respective terminal to corresponding contacts of the thirdand fourth microelectronic elements for carrying the respective signalthereto, wherein the signal carried by the first, second, third andfourth connections is subject to propagation delay of the same durationbetween the respective terminal and each of the corresponding contactscoupled thereto. In accordance with a particular aspect, the parallelaxes can be first parallel axes, and the substrate can further includethird and fourth apertures which extend between the first and secondsurfaces. The third and fourth apertures can have long dimensions havinglengths extending along second axes parallel to one another, the secondparallel axes being transverse to the first parallel axes, wherein thecentral region is bounded at least partly by the third and fourthapertures, and the connections include leads having portions alignedwith at least one of the third or fourth apertures.

In accordance with a particular aspect of the invention, each of thefirst, second, third and fourth microelectronic elements is configuredto provide predominantly a memory storage function.

In accordance with a particular example, third and fourthmicroelectronic elements can be affixed with the packaging structure,wherein at least one of the groups of connections includes third andfourth connections electrically coupling the respective terminal tocorresponding contacts of the third and fourth microelectronic elementsfor carrying the respective signal thereto. The first, second, third andfourth connections can be configured such that the signal carried by thefirst, second, third and fourth connections is subject to propagationdelay of the same duration between the respective terminal and each ofthe corresponding contacts coupled thereto. In a particular example, thecentral region of the face can be bounded by first parallel axes andsecond parallel axes transverse to the first parallel axes. Each firstaxis may bisect an area of one of the first and second microelectronicelements, respectively, and may extend in a direction parallel to firstand second opposed edges of each of the first and second microelectronicelements. Each second axis may bisect an area of one of the third andfourth microelectronic elements, respectively, and may extend in adirection parallel to first and second opposed edges of each of thethird and fourth microelectronic elements.

In accordance with a particular aspect of the invention, the packagingstructure may include a substrate having contacts at a surface facingthe microelectronic elements, the contacts of the microelectronicelements facing the substrate contacts and joined thereto. In accordancewith a particular example, each of the first parallel axes mayintersects exactly one of the third or fourth microelectronic elements,and each of the second parallel axes may intersect exactly one of thefirst or second microelectronic elements.

In accordance with a particular aspect of the invention, themicroelectronic package may further include a circuit panel having panelcontacts adjacent and electrically connected to the terminals, thecircuit panel having conductive elements thereon which provide delaymatching, such that signals carried by each group of connections to themicroelectronic elements are subject to delay of the same durationthrough the packaging structure and the circuit panel.

In accordance with a particular aspect of the invention, the first andsecond microelectronic elements can be spaced apart from one another ina direction parallel to the face of the packaging structure.

In accordance with a particular aspect of the invention, the packagingstructure may include a substrate having at least one aperture extendingthrough the substrate, and the second microelectronic element maypartially overlie the first microelectronic element such that contactsof the second microelectronic element are disposed beyond an edge of thefirst microelectronic element, wherein the connections to thecorresponding contacts of the second microelectronic element includeleads having portions aligned with the at least one aperture.

In accordance with a particular aspect of the invention, the leads caninclude wire bonds which extend through the at least one aperture.

In accordance with a particular aspect of the invention, the at leastone aperture may include first and second bond windows, and theconnections can include first leads coupled to the first microelectronicelement having portions aligned with the first bond window, and secondleads coupled to the second microelectronic element having portionsaligned with the second bond window.

In accordance with a particular aspect of the invention, at least someof the terminals with which the first and second leads are coupled canbe disposed between the first and second bond windows.

In accordance with a particular aspect of the invention, the firstmicroelectronic element may have contacts at a front face thereof and arear face opposed to the front face. The rear face may be mounted to thepackaging structure, and the leads may include wire bonds connectedbetween the contacts and the packaging structure.

In accordance with a particular aspect of the invention, at least one ofthe first or second microelectronic elements may include a memorystorage array and at least one of the first or second microelectronicelements may include a microcontroller.

In accordance with a particular aspect of the invention, the packagingstructure may include a dielectric layer formed on the contact-bearingsurfaces of the first and second microelectronic elements, tracesextending in a direction parallel to the dielectric layer, and metalizedvias extending at least partly through a thickness of the dielectriclayer and electrically coupled with the contacts of the first and secondmicroelectronic elements, wherein the terminals are electricallyconnected to the contacts by the traces and the vias.

A method of making a microelectronic package according to an aspect ofthe invention can include forming electrical connections coupling firstand second microelectronic elements with packaging structure having aplurality of terminals disposed at a face thereof, the terminals beingconfigured for connecting the microelectronic package to at least onecomponent external to the package. The connections can include groups ofconnections for carrying respective signals, each group including two ormore connections, e.g., a first connection extending from a respectiveterminal of the package to a corresponding contact on the firstmicroelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element. The first and second connections can beconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto.

In accordance with a particular aspect of the invention, the packagingstructure may have edges bounding the face, and the face may have acentral region occupying a central portion thereof, and a second regionoccupying a portion of the face between the central portion and at leastone of the edges. The terminals can include first terminals exposed atthe central region and second terminals exposed at the second region.The groups of connections may couple the first terminals with thecorresponding contacts, and the microelectronic package can includefurther connections electrically coupling the second terminals withcontacts of the microelectronic elements.

In accordance with a particular aspect of the invention, the packagingstructure can include a substrate having at least one aperture extendingthrough the substrate, and the second microelectronic element maypartially overlie the first microelectronic element. In such way,contacts of the second microelectronic element can be disposed beyond anedge of the first microelectronic element. Connections to thecorresponding contacts of the second microelectronic element may includeleads having portions aligned with the at least one aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a timing diagram illustrating skew in the arrival of signalsin accordance with the prior art.

FIG. 1A is a sectional view illustrating a microelectronic packageaccording to an embodiment of the invention.

FIG. 1B is plan view looking towards a terminal-bearing or bottomsurface of a package in accordance with an embodiment of the invention.

FIG. 1C is a sectional view illustrating a microelectronic packageassembled with a circuit panel according to an embodiment of theinvention.

FIG. 1D is a sectional view illustrating a microelectronic packageaccording to a variation of the embodiment of the invention shown inFIGS. 1A-1C.

FIG. 1E is partial fragmentary view illustrating beam lead electricalconnections according to particular implementations of the embodimentshown in FIGS. 1A-1C.

FIG. 2 is a plan view illustrating an arrangement of a central regionand peripheral regions and terminal assignments of signals thereinaccording to an embodiment of the invention.

FIG. 3 is a plan view illustrating electrical connections betweenrespective terminals and contacts of each of first and secondmicroelectronic elements according to an embodiment of the invention.

FIG. 4 is a timing diagram illustrating operation of a microelectronicpackage in accordance with an embodiment of the invention.

FIGS. 5A and 5B are a plan view and a corresponding sectional view of amicroelectronic package according to a variation of the embodiment shownin FIGS. 1A-1C.

FIG. 5C is a sectional view of a microelectronic package according to avariation of the embodiment shown in FIGS. 1A-1C.

FIGS. 6A and 6B are a plan view and a corresponding sectional view of amicroelectronic package according to a variation of the embodiment shownin FIGS. 1A-1C.

FIG. 6C is a sectional view of a microelectronic package according to avariation of the embodiment shown in FIGS. 6A and 6B.

FIGS. 7A and 7B are a plan view and a corresponding sectional view of amicroelectronic package according to a variation of the embodiment shownin FIGS. 1A-1C.

FIG. 8 is a sectional view of a microelectronic package according to avariation of the embodiment shown in FIGS. 7A and 7B.

FIG. 9A is a plan view looking towards a bottom surface of amicroelectronic package according to a variation of the embodiment shownin FIGS. 1A-1C.

FIG. 9B is a sectional view through line 9B-9B of FIG. 9A.

FIG. 9C is a sectional view through line 9C-9C of FIG. 9A.

FIG. 9D is a sectional view through line 9D-9D of FIG. 9A.

FIG. 9E is a sectional view through line 9E-9E of FIG. 9A.

FIG. 10 is a plan view further illustrating an arrangement of terminalswithin an embodiment of the invention as shown in FIGS. 9A-9E.

FIG. 11 is a plan view illustrating relative locations ofmicroelectronic elements in a variation of an embodiment illustrated inFIGS. 9A-9E and 10.

FIG. 12 is a plan view illustrating relative locations ofmicroelectronic elements in a variation of an embodiment of FIGS. 9A-9Eand 10.

FIG. 13 is a plan view illustrating relative locations ofmicroelectronic elements in a variation of an embodiment of FIG. 12.

FIG. 14 is a plan view illustrating relative locations ofmicroelectronic elements in a variation of an embodiment of FIG. 13.

FIG. 15 is a plan view illustrating relative locations ofmicroelectronic elements in a variation of an embodiment of FIG. 11.

FIG. 16 is a schematic sectional view illustrating a system according toan embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention herein provide packages which have morethan one semiconductor chip, i.e., a microelectronic element therein. Amultiple chip package can reduce the amount of area or space required toconnect the chips therein to a circuit panel, e.g., printed wiring boardto which the package may be electrically and mechanically connectedthrough an array of terminals, such as a ball grid array, land gridarray or pin grid array, among others. Such connection space isparticularly limited in small or portable computing devices, e.g.,handheld devices such as “smartphones” or tablets which typicallycombine the function of personal computers with wireless connectivity tothe broader world. Multi-chip packages can be particularly useful formaking large amounts of relatively inexpensive memory available to asystem, such as advanced high performance dynamic random access memory(“DRAM”) chips, e.g., in DDR3 type DRAM chips and its follow-ons.

The amount of area of the circuit panel needed to connect the multi-chippackage thereto can be reduced by providing common terminals on thepackage through which at least some signals travel on their way to orfrom two or more chips within the package. However, doing so in a waythat supports high performance operation presents challenges. To avoidundesirable effects such as noise and propagation delays within thepackage, the traces, vias, and other conductors which electricallyconnect the terminals at the exterior of the package with the chipstherein must not be too long or too narrow in order to avoid excessiveinductance and stub length, and must not have excessive capacitance.Heat dissipation also presents a challenge for advanced chips, such thatit is desirable for at least one of the large flat surfaces of each chipto be coupled to a heat spreader or be exposed to or in thermalcommunication with a flow or air within an installed system. Thepackages described below can help to further these goals.

Embodiments of the invention herein provide ways of de-skewing signalscarried within microelectronic packages that have at least twomicroelectronic elements, wherein each of a plurality of microelectronicelements in the package transmits or receives some of the same signalsthrough a set of common terminals of the package. Thus, correspondingcontacts of multiple chips within the package can be electricallyconnected with a single common terminal of the package which isconfigured for connection with a component external to the package,e.g., a circuit panel such as printed circuit board, externalmicroelectronic element or other component.

The structures and processes herein help to achieve a de-skewed timingof a signal from a common package terminal to contacts on more than onechip through one or more of the following: placement of at least somecommon terminals of the package used for carrying time-varying signalsin a region of the package between at least two of the chips; and designof traces or other conductors of the package such that the signalpropagation delay between each common terminal and the correspondingcontacts of each chip connected thereto is the same, i.e., within alimited tolerance.

FIGS. 1A-B illustrates a particular type of microelectronic assembly orpackage 10 in which de-skewing of signals can be achieved according toan embodiment of the invention. As seen therein, the package 10 includesa first microelectronic element 12 having a front face 16 and aplurality of electrically conductive contacts 20 at a front facethereof. For example, as illustrated in FIGS. 1A-B, contacts 20 can bearranged in one or more rows disposed in a central region 13 of thefront face 16 which occupies a central portion of an area of the frontface. The central region 13, for example, may occupy an area of thefront face which includes a middle third of the shortest distancebetween opposed peripheral edges 27, 29 of the first microelectronicelement. In one example, first and second microelectronic elements canbe bare chips or microelectronic units each configured to predominantlyprovide memory storage array function. Thus, in one example, eachmicroelectronic element can incorporate a dynamic random access memory(“DRAM”) storage array or which is configured to predominantly functionas a DRAM storage array. Such “memory” microelectronic element or“memory chip” may have a greater number of active circuit elements,e.g., active semiconductor devices, which are configured to providememory storage array function than any other function of themicroelectronic element.

The package includes packaging structure, for example, an optionalsubstrate 30 with terminals 36, e.g., conductive pads 36, lands orconductive posts thereon. In some cases, the substrate may consistessentially of a material having a low coefficient of thermal expansion(“CTE”), i.e., a CTE of less than 10 parts per million per degreeCelsius (hereinafter, “ppm/° C.”), such as a semiconductor materiale.g., silicon, or a dielectric material such as ceramic material orsilicon dioxide, e.g., glass. Alternatively, the substrate may include asheet-like dielectric element which can consist essentially of apolymeric material such as polyimide, epoxy, thermoplastic, thermosetplastic, or other suitable polymeric material or which includes orconsists essentially of composite polymeric-inorganic material such as aglass reinforced structure of BT resin (bismaleimide triazine) orepoxy-glass, such as FR-4, among others. Electrical connections betweenthe contacts 20 and terminals 36 can include optional leads, e.g., wirebonds 72, 74, or other possible structure in which at least portions ofthe leads are aligned with an aperture extending between surfaces 32, 34of the substrate. For example, as seen in FIG. 1E, the connections caninclude a beam lead 73 which extends along a surface 34 of the substratewhich faces microelectronic element 12, such lead extending beyond anedge of the substrate or extending beyond an edge of an aperture 33 inthe substrate, and joined to the contact 20. Alternatively, a beam lead75 joined to contact 20 may instead extend along a surface 32 of thesubstrate which faces away from microelectronic element 12.

The terminals 36 function as endpoints for the connection of themicroelectronic package 10 with corresponding electrically conductiveelements of an external component such as a circuit panel, e.g., printedwiring board, flexible circuit panel, socket, other microelectronicassembly or package, interposer, or passive component assembly, amongothers. In a particular example, the terminals of the package 10 mayinclude joining elements 38, e.g., conductive masses such as solderballs, masses of conductive material, such as conductive paste,conductive matrix material, or conductive adhesive attached to theterminals.

As further seen in FIG. 1A, the package 10 can further include a secondmicroelectronic element 14 having a front face 22 with a plurality ofcontacts 26 thereon. In the particular example of FIG. 1A, the contacts26 of the second microelectronic element 14 are disposed beyond aperipheral edge 29 of the first microelectronic element. This permitselectrical connections between the contacts 26 and the terminals 36 toinclude leads, e.g., wire bonds 52, 54 extending from the contacts 26 ofthe second microelectronic element 14 at least partially within anaperture 39 or gap of the packaging structure 10. In a particularembodiment, the leads joined to contacts 26 can be arranged as shown anddescribed above relative to FIG. 1E. In one example, contacts 26 of thesecond microelectronic element 14 can be disposed within a centralregion 14A of the front face 28 thereof, the central region beingseparated from peripheral edges 40 and 42 by peripheral regions 14B and14C of the second microelectronic element.

In a particular embodiment as seen in FIG. 1A, the packaging structuremay define apertures or gaps 33, 39 within which or through which leadssuch as wire bonds 72, 74 or other types of electrical connections maybe aligned. For example, as seen in FIGS. 1A-B, apertures 33, 39 canextend between first and second opposed surfaces 32, 34 of a substrate30. In the example of FIGS. 1A-B, leads 72 74 can have portions alignedwith the apertures 33, 39. In one embodiment, as seen in FIG. 1A, theleads can include or be wire bonds or beam leads extending from contacts20 of first microelectronic element 12, or from contacts 26 of secondmicroelectronic element 14 to conductive elements 40 at surface 32 ofthe substrate. The conductive elements can be further connected with theterminals 36.

In a particular embodiment, the leads can include or be beam leads 73which extend along a surface 34 of the substrate which faces the surface16, 22 of the first or second microelectronic elements, or bothmicroelectronic elements and extends beyond an edge of an aperture 33 or39 to contacts 20 or contacts 26 or both. In another embodiment, beamleads 75 can extend along a surface 32 of the substrate at the face ofthe packaging structure. In one embodiment, beam leads 73 and 75 canexist in the same package. An encapsulant 82 may optionally cover atleast a portion of the leads and extend into the apertures or gaps ofthe packaging structure.

As further seen in FIG. 1A, the package may further include a thirdelement such as a spacer 31 or other element between the secondmicroelectronic element 14 and substrate 30. In one embodiment, thethird element can be an element which has a low coefficient of thermalexpansion (“CTE’) such as an element having a low CTE of less than 10parts per million per degree Celsius (hereinafter, “ppm/° C.”. In oneembodiment, the third element can consist essentially of semiconductor,glass, or ceramic material, or may consist essentially of liquid crystalpolymer material or a filled polymeric material which includes filledparticles which have a low CTE.

The package may further include an adhesive 60 between the adjacentfaces of the first and second microelectronic elements 12, 14, and anencapsulant 62 contacting edge surfaces 27, 29, 40, 42. The encapsulantmay optionally cover, partially cover, or leave uncovered the rearsurfaces 15, 24 of the microelectronic elements 12, 14. For example, inthe package shown in FIG. 1A, encapsulant 62 can be flowed, stenciled,screened or dispensed onto rear surfaces 15, 24 of the microelectronicelements. In another example, the encapsulant can be a mold compoundwhich is formed thereon by overmolding.

As depicted in the bottom plan view of the microelectronic package 10 inFIG. 1B, locations of central terminals 36 are disposed in acorresponding central region 44 of the substrate. The central region 44occupies area of the surface of the substrate between the apertures 33,39. Peripheral regions 46, 48 of the substrate which can be disposedbetween the respective apertures 33, 39 and the edges 132, 134 of thesubstrate can accommodate peripheral terminals 136, 137, respectively.

In the embodiment of FIGS. 1A-B, at least some signals which passthrough the central terminals 36 of the package are common to bothmicroelectronic elements. These signals are routed through connectionssuch as conductive traces extending in a direction parallel to thesurface 32 of the substrate from the terminals 36 to the correspondingcontacts 20, 26 of the first and second microelectronic elements 12, 14.For example, as shown in FIG. 1B, terminal 36A, one of many terminals 36disposed in a central region 44 of the substrate surface 32, can beelectrically connected with conductive contact 20A of the firstmicroelectronic element 12 through a conductive trace 51A, conductiveelement 40A, e.g., a bond pad, and a wire bond 74A joined to the contact40A and the contact 20A of the first microelectronic element 12.Terminal 36A can also be electrically connected with conductive contact26A of the second microelectronic element 14 through a conductive trace53A, conductive element 40B, e.g., a bond pad, and a wire bond 52Ajoined to the contact 40B and contact 26A of the second microelectronicelement 14.

Referring to FIG. 1C, the terminals of the package can be joined tocorresponding contacts 71 of an external component such as a circuitboard 70 through joining element 38. In the specific arrangement herein,microelectronic package 10 routes a signal which is common to multiplemicroelectronic elements 12, 14 through a common central terminal 36A ofthe package, rather than through two or more terminals of the packageeach dedicated to a specific one of the microelectronic elements. Inthis way, an amount of area of the package substrate 30 occupied by suchterminals can be reduced.

FIG. 1D illustrates a microelectronic package 110 according to avariation of the above-described embodiment in which the packagingstructure includes a dielectric layer 90 formed on surfaces of the firstand second microelectronic elements 12, 14, and metallized vias 92electrically coupled to contacts 20, 26 of the microelectronic elementsand extending at least partially through a thickness of the dielectriclayer. Electrically conductive traces 94 extend in one or moredirections which are typically parallel to a surface 93 of thedielectric layer and electrically connect the metallized vias withterminals 36, 136, 137. The traces may be formed integrally with themetalized vias, and some or all traces and vias may include portions ofa single monolithic metal layer, e.g., portions of a single layer ofdeposited metal, such as a layer of metal plated or otherwise deposited(e.g., screen-printed, stenciled, dispensed, etc.), onto the dielectriclayer 90 and into openings in the dielectric layer to form themonolithic metal layer of which the traces and vias are made.

The package 110 may be a fan-out wafer-level package having a land gridarray (“LGA”) or ball grid array (“BGA”) style connection arrangement ofterminals thereon. The package 110 may have an encapsulant 62 extendingbeyond edges 27, 42 of the microelectronic elements 12, 14. Theencapsulant 62 may be an overmold which has a surface 17 co-planar withor generally co-planar with a contact-bearing surface 16 of firstmicroelectronic element 12. The dielectric layer 90 may overlie theencapsulant 62 and some of the terminals or traces can overlie theencapsulant 62.

Package 110 may be made according to techniques as described in one ormore embodiments described in commonly owned U.S. application Ser. No.12/953,994 filed Nov. 24, 2010, the disclosure of which is incorporatedby reference herein. However, specific features, e.g., relative tracelengths, relative propagation delay between a terminal and correspondingcontacts coupled thereto, and assignment and placement of packageterminals for carrying particular signals are as described herein.

As further shown in FIG. 1D, package 110 may further includeelectrically conductive pillars 96, e.g., deposited, joined, bonded oretched metallic or metal-containing structures which effectively providecontacts raised above the contact-bearing surface 25 of the secondmicroelectronic element. In a particular embodiment, although not shown,such pillars can also be provided on contacts 20 of the firstmicroelectronic element. As shown in FIG. 1D, the metallized vias 92 canbe coupled to the contacts 26 through pillars 96.

Referring to FIG. 2, signals which are best routed through the centralterminals (in central region 44) are signals which are utilized by eachmicroelectronic element for operations performed in common by bothmicroelectronic elements. In the above-described example in which firstand second microelectronic elements 12, 14 each incorporates a DRAMstorage array, address signals are utilized for common operationsperformed by the microelectronic elements, and are routed through commoncentral terminals when possible. Signals which time operations such asaddress signals, clock signals, strobes, e.g., row address strobe,column address strobe, and write enable signals are also utilized forcommon operations and are best routed through central terminals whichare common to the microelectronic elements within the package 10. Suchsignals can be used to sample the signals which enter or exit eachmicroelectronic element 12, 14. Other electrical connections which donot involve critical timing paths and which can be routed through theperipheral terminals in peripheral regions 46, 48 of the substrate 30include data signals, e.g., bi-directional data input-output signals,data strobes, connections to power and ground, column select signals andclock enable signals. By way of example, a clock enable signal can beused when active to switch a microelectronic element into an activeoperating mode when needed to perform operations, and alternatively wheninactive can be used to switch the microelectronic element into aninactive operating mode, e.g., a standby mode or quiesced mode, when themicroelectronic element is not needed to perform operations.

However, even when signals are routed through common central terminals,the structure can be configured further to de-skew the signals whichpass therethrough to and from each microelectronic element. Signalde-skewing can be provided by ensuring that the electrical connectionsbetween each common terminal and contacts on each microelectronicelement connected thereto have matched delays such that the signalcarried on each of the electrical connections is subject to propagationdelay of the same duration between the respective common centralterminal and the corresponding contacts on each of the first and secondmicroelectronic elements.

One way that matched propagation delays can be achieved between a commonterminal and each microelectronic element is to structure the traces andother conductive elements on each path or connection from the commonterminal to the respective microelectronic element (e.g., as seen inFIG. 1B, one path or a first connection including conductive elements51A, 40A and 74A, and another path or second connection includingconductive elements 53A, 40B and 52A), such that a signal carried by thefirst and second connections in the group of connections extending fromthe respective common terminal is subject to propagation delay of thesame duration between the respective terminal and each of thecorresponding contacts which are coupled to such terminal. To someextent, the delays on different paths or different connections extendingfrom the common terminal are functions of the lengths of the respectivepaths or connections. Therefore, in some cases, the delays can be madethe same by structuring the paths to have the same lengths. However, thepropagation delays are also functions of the inductance, capacitance,and resistance on each path, and effects due to proximity of otherconductive features adjacent to each path. Therefore, these additionalfactors must also be considered when structuring the conductive elementswhich make up the paths or connections. When the delays on each path orconnection through a particular common terminal to correspondingcontacts are the same, the paths can be said to have the same “totalelectrical lengths.”

FIGS. 3 and 4 further illustrate the above-described principles. As seenin FIG. 3, common terminals 36A-36B, through which clock signals travelto contacts of respective microelectronic elements 12, 14 (denoted CHIP1and CHIP2 in FIG. 3), can be centered within the central region 44 ofthe substrate. In this way, the lengths of paths 80, 82 to the contacts20, 26 of the respective microelectronic elements can be the same withinan allowed tolerance therefor. In one example, the tolerance can be 10%of the cycle time of a clock signal used to sample signals input to themicroelectronic elements 12, 14. In another example, the tolerance canbe smaller, such as 5% of the cycle time of the clock signal used tosample signals input to the microelectronic elements 12, 14. FIG. 4illustrates that the clock signals received at the respective contacts20, 26 of each chip (20 or 26, respectively) transition between high andlow levels at a particular point in time t_(CK).

FIG. 3 further illustrates the paths 84 and 86 which electricallyconnect a terminal 36C with the contacts 20, 26 of the respectivemicroelectronic elements CHIP1 and CHIP2. Here, the paths 84, 86 need tobe structured differently because the terminal 36C is closer to thecontact 26 of CHIP2 than it is to contact 20 of CHIP1. Accordingly,while path 84 may be relatively straight, path 86 has jogs therein whichincrease its length. In this way, the total electrical lengths of thepaths 84, 86 can be made the same, i.e., the same within tolerance. As aresult, an address1 signal that is received at terminal 36C reachescontacts of each microelectronic element at the same time t_(CK) as seenin FIG. 4. Note that in the example with terminal 36C, the lengths ofthe paths 84, 86 can be the same within tolerance, even when thestraight line distances between terminal 36C and the contacts 20, 26 towhich it is electrically connected are much greater than the tolerancetherefor.

In addition, when the paths include wire bonds and traces, the length ofthe wire bond can be increased for the path which includes a shortertrace, or the length of the wire bond can be decreased for the pathwhich includes a longer trace.

In another example, the degree of shielding which exists for a path in apackage can be selectively reduced to reduce the delay on one pathrelative to another path, or can be selectively increased to increasethe delay on a path relative to another path. For example, if thepackage includes a ground or power plane overlying conductors of therespective paths, a portion of such ground or power plane can be removedoverlying one conductor such that a portion of the length of suchconductor is unshielded, therefore reducing capacitance between suchconductor and the ground or power plane. In this way, the reducedcapacitance for the unshielded portion of the conductor has an effect ofreducing the delay on such conductor.

In addition alternatively, an air gap can be created where appropriateto decrease the delay along a particular path, or the dielectricconstant at a particular location of the substrate can be varied byallowing a particular dielectric material having a different dielectricconstant, e.g., an encapsulant, solder mask, etc. to flow into locationduring fabrication.

FIGS. 5A-5B illustrate a microelectronic package according a variationof the above-described embodiment (FIGS. 1A-1C) in which first andsecond microelectronic elements 212, 214 are spaced apart from oneanother and each bonded to the substrate. In this case, there is a space238 on the substrate 230 which is uncovered by either the first orsecond microelectronic elements 212, 214, the space 238 disposed betweenperipheral edges 229, 240 of the microelectronic elements 212, 214. FIG.5A illustrates that terminals 236 and the paths between them andrespective microelectronic elements can be arranged according to theprinciples described above to achieve matched delays for each pair ofelectrical connections from a common central terminal 236, such as inthe example shown at 236A.

FIG. 5C illustrates a variation in which each microelectronic element312, 314 has contacts disposed adjacent a peripheral edge 332 thereof,and wire bonds 352 to each microelectronic element extend through thesame aperture 333. The paths between the terminals and respectivemicroelectronic elements can be arranged according to the principlesdescribed above to achieve matched delays for each pair of electricalconnections from a common terminal 336 on the package.

FIGS. 6A-6B illustrates a further variation in which eachmicroelectronic element 412, 414 is mounted face-up above the substrate430 such that wire bonds 452 extend between contacts on themicroelectronic elements to contacts (not shown) exposed at a surface434 of the substrate opposite the terminals. In this case, commonterminals 436A can be disposed at peripheral regions of the substratesurface 432 outside areas over which the microelectronic elements aredisposed. In addition or alternatively, terminals can be disposed inregions of the substrate surface which underlie the microelectronicelements, as in the case of terminal 436B, or in regions between themicroelectronic elements, as in the case of terminal 436C. Again, thepaths between common terminals 436 and respective microelectronicelements can be arranged according to the principles described above toachieve matched delays for each pair of electrical connections from acommon terminal 436 on the package. For example, as indicated above, thetotal electrical lengths of the connections from a respective terminalto the contacts to which it is coupled can be made the same.Alternatively or in addition thereto, selective shielding or other meansas described above can be used to achieve matched delays on theconnections between a respective terminal and the contacts of each ofthe microelectronic elements coupled to such terminal.

FIG. 6C illustrates a further variation in which each microelectronicelement 512, 514 is mounted face-up on the substrate and eachmicroelectronic element has contacts disposed along a peripheral edge532 thereof. Wire bonds 552 to each microelectronic element extendbeyond adjacent edges 532 of the microelectronic elements. The pathsbetween the terminals and respective microelectronic elements can bearranged according to the principles described above to achieve matcheddelays for each pair of electrical connections from a common terminal536 on the package.

FIGS. 7A-7B illustrate a further variation in which each microelectronicelement 612, 614 is flip-chip mounted to the substrate such that eachmicroelectronic element has contacts 620 facing corresponding substratecontacts 640 on a surface 634 of the substrate, being joined thereto,such as through a joining element 642 such as a solder bump or otherelectrically conductive mass or joint 642. The paths between theterminals and respective microelectronic elements can be arrangedaccording to the principles described above to achieve matched delaysfor each pair or group of electrical connections from a common terminal636 on the package to corresponding contacts on each of the first andsecond microelectronic elements 612, 614.

FIG. 8 illustrates a variation of the embodiment shown in FIGS. 7A-7B inwhich a stacked assembly 790 of microelectronic elements 712, 714 cantake the place of one or more of the microelectronic elements 612, 614.Microelectronic elements 712 and 714 can be of the same or differenttypes. In this case, electrical connections between microelectronicelements within each stacked assembly can include through silicon vias730, or edge connections (not shown) extending along one or more edgesor peripheral edges of the assembly, or a combination thereof. Eachmicroelectronic assembly can be a stacked assembly of unpackagedsemiconductor chips or can be a stacked and electrically connectedassembly of individually packaged chips.

FIG. 9A illustrates a further variation in which microelectronic package800 includes first, second, third and fourth microelectronic elementswhich are disposed as shown therein. In a particular example, eachmicroelectronic element can be a DRAM chip or can incorporate a DRAMstorage array. In another example, the chips can include another type ofmemory which may be non-volatile such as flash memory. First and secondmicroelectronic elements 812, 814 can be spaced apart and mounted to asurface of the substrate, with third and fourth microelectronic elements816, 818 partially overlying the first and second microelectronicelements. The third and fourth microelectronic elements 816, 818 can bespaced apart from one another, each at least partially overlying thefirst and second microelectronic elements. Apertures, e.g., bondwindows, extending through the substrate in a direction of a thicknessof the substrate are shown at 833, 839, 843, and 849. Microelectronicpackage 800 can be arranged and fabricated in a manner similar to anembodiment (FIGS. 7-9) described in commonly owned U.S. ProvisionalApplication 61/477,877 filed Apr. 21, 2011, the disclosure of which isincorporated by reference herein, although specific features, e.g.,relative trace lengths, relative propagation delay between a terminaland corresponding contacts coupled thereto, and assignment and placementof package terminals for carrying particular signals are as describedherein.

As best seen in FIG. 9A, first and second apertures 833, 839 can bearranged such that the longest dimensions of the apertures, i.e., thelengths of the apertures 833, 839, extend along first parallel axesdefined by line 9C-9C and line 9E-9E. As further seen, these firstparallel axes 9C, 9E, in which the lengths of apertures 833, 839 extendare transverse to second parallel axes 850, 852 in which the longestdimensions (the lengths) of apertures 843, 849. The apertures 843, 849can be disposed beyond respective opposite edges 820, 822 of the firstand second microelectronic elements 816, 818. In this way, leads 74(FIG. 9C) can be electrically coupled with contacts 826 of the third andfourth microelectronic elements, the leads 74 having portions alignedwith the apertures 843, 849. As described above relative to FIGS. 1A-D,the leads 74, as well as the leads 72 connected to the contacts of thefirst and second microelectronic elements 812, 814 (FIG. 9B) can includeor can be wire bonds or beam leads.

FIG. 9B is a sectional view of microelectronic package through line9B-9B of FIG. 9A. As seen therein, first and second microelectronicelements can be spaced apart from one another, with contact-bearingsurfaces 16 thereof facing the substrate, and leads 72 having portionsaligned with the apertures 833, 839. As seen in FIG. 9A, an axis 9C-9C,along which the length of aperture 833 extends, can intersect apertures849, 843. As further seen in FIG. 9A, axis 9E-9E, extending in adirection of the length of aperture 839, can intersect apertures 843 and849. FIG. 9D is a view of the package through line 9E-9E of FIG. 9A. Theposition of first microelectronic element 812 within the package isshown in relief using a dashed line, as the section along line 9D-9D(See FIG. 9A) runs between the first and second microelectronicelements.

The positions of a central region and a second or peripheral region ofthe substrate 830 of FIGS. 9A-9E are further illustrated in FIG. 10. Thecentral region 870 has boundaries as shown at 860, the central regionbeing bounded by the apertures (e.g., bond windows) 853, 855, 857, 859,or more specifically, the longest dimensions of the apertures. Firstterminals 36 typically are distributed throughout the central region,each of at least some of the first terminals being electrically coupledto contacts of two or more of the microelectronic elements 812, 814,816, 818. As discussed above, the first terminals and the electricalconnections between the first terminals and the contacts can be used tocarry timing critical signals, such as clock signals, address signals,and command signals.

Second terminals 136 typically are distributed throughout a peripheralregion 872 of the substrate disposed beyond edges of the central region870. The peripheral region can be disposed beyond apertures 853, 855,857, 859, being bounded by edges 832, 834 of the substrate and edges ofthe apertures as illustratively shown at 862. Typically, a secondterminal connects only to a single contact of a single microelectronicelement, although exceptions of course exist. The need to arrangestructure within the package to de-skew signals carried by the secondterminals, i.e., to make propagation delays the same from secondterminals to the contacts the same, is not critical. This is becauseconductive elements on a circuit panel or board to which the package isconnected can be arranged to selectively provide de-skewing toindividual ones of the second terminals where needed. However, it ispossible for a second terminal to be electrically coupled to more thanone contact of a microelectronic element 812, 814, 816 or 818 within thepackage, or to corresponding contacts on more than one of themicroelectronic elements. In this case, the potential, e.g., power orground, or the signal carried by such second terminal can be one whichis less sensitive to differences in arrival times of the potential orsignal, i.e., to “skew”, and therefore, no special arrangement may beneeded on the package to compensate for the skew.

FIG. 11 illustrates a variation of the embodiment described aboverelative to FIGS. 9A-9D and 10, in which the central region 950 has beenenlarged by spacing the micro-electronic elements farther apart from oneanother. The terminals and leads thereon are similar to those describedabove and can be omitted from the figure for clarity. Dashed line 960marks a boundary between the central region 950 and the peripheralregion 952. As in the embodiment of FIGS. 9A-9D and 10, the centralregion 960 can be disposed between edges 944, 946 which define thelongest dimensions of the apertures 933, 939, 943, 949. The peripheralregion occupies area of the substrate beyond the central region. In anarrangement as seen in FIG. 11, the central region may in some caseshave larger area than the peripheral region so as to allow for a greaternumber of terminals to be arranged in the central region. As discussedabove, the configurations discussed above for de-skewing of signals fromshared terminals, i.e., for providing matched delays, can be implementedfor shared terminals within such central region.

FIG. 12 illustrates a particular arrangement of microelectronic elements1012, 1014, 1016, 1018, on a substrate similar to the shape of apinwheel. Again, the terminals and leads thereon are similar to thosedescribed above and can be omitted from the figure for clarity. In thiscase, the longest dimensions of apertures 1043, 1049 define firstparallel axes 1050, 1052, and the longest dimensions of apertures 1033,1039 define second parallel axes 1054, 1056. The second parallel axesare transverse to the first parallel axes. In the particular exampleshown in FIG. 12, when the contacts 1020 of each microelectronic elementare arranged in a central region of the microelectronic element, thecontacts 1020 can be arranged along an axis 1050 which bisects an areaof a contact-bearing face of the microelectronic element 1012.Alternatively, the contacts 1020 can be arranged otherwise in one ormore parallel columns of contacts which extend parallel to the axis1050. Axis 1050 intersects the area of exactly one other microelectronicelement in package 1000, that is, axis 1050 intersects the area ofmicroelectronic element 1018. Similarly, an axis 1052 which bisects anarea of the contact-bearing face of microelectronic element 1016 canintersect the area of exactly one other microelectronic element 1014.The same is also true of axis 1054 which can bisect the area of thecontact-bearing face of the microelectronic element 1014 and intersectthe area of exactly one other microelectronic element 1012. Indeed, thisis also true of a similarly defined axis 1056 of microelectronic element1018 which intersects the area of exactly one other microelectronicelement 1016.

The arrangement of microelectronic elements 1012, 1014, 1016, 1018 onsubstrate 1030 defines a central region 1070 of the substrate having aboundary generally as shown by dashed line 1072, i.e., a rectangulararea that is bounded by the apertures 1033, 1039, 1043, and 1049.Peripheral region 1074 lies outside of boundary 1072. The arrangementshown in FIG. 12 can be a particularly compact arrangement like thatshown in FIGS. 9A-9D and 10, except that in FIG. 12 each microelectronicelement is disposed adjacent to the substrate rather than partiallyoverlying another microelectronic element as in the case ofmicroelectronic elements 816, 818 of FIGS. 9A-9D. Thus, the arrangementcan provide a compact arrangement of microelectronic elements and arelatively expansive central region without requiring a microelectronicelement to overlie any other microelectronic element.

In variations of the embodiments described above it is possible for thecontacts of microelectronic elements to not be disposed in centralregions of the surfaces thereof. Rather, the contacts may be disposed inone or more rows adjacent an edge of such microelectronic element. Inanother variation, the contacts of a microelectronic element can bedisposed adjacent two opposed edges of such microelectronic element. Inyet another variation, the contacts of a microelectronic element can bedisposed adjacent any two edges, or be disposed adjacent more than twoedges of such microelectronic element. In such cases, locations ofapertures in the substrate can be modified to correspond to suchlocations of the contacts disposed adjacent such edge or edges of themicroelectronic element.

FIG. 13 illustrates a variation of the embodiment shown in FIG. 12, inwhich apertures in the packaging structure are omitted. First parallelaxes 1150, 1152 bisect the total areas of the contact-bearing faces ofthe microelectronic elements 1112, 1116 and extend in directionsparallel to the peripheral edges 1160 of those microelectronic elements.Second parallel axes 1154, 1156 bisect the total areas of thecontact-bearing faces of microelectronic elements 1114, 1118 and extendin directions parallel to the peripheral edges 1162 of thosemicroelectronic elements. As in the embodiment of FIG. 12, and each axisintersects the area of exactly one microelectronic element other thanthe microelectronic element it bisects.

In one embodiment, the packaging structure may include a dielectriclayer formed on surfaces of the microelectronic elements and conductivestructure defining a redistribution layer thereon, such as describedabove relative to FIG. 1D. For example, metallized vias can be coupledto the contacts of each microelectronic element, and conductivestructure, e.g., traces, can be electrically coupled to the metallizedvias and the terminals of the package.

In another embodiment, the packaging structure can include a substratehaving substrate contacts on a surface of the substrate. Correspondingcontacts of the microelectronic elements can be arranged such that thecontacts face the substrate contacts and be joined thereto in aflip-chip configuration, such as with conductive masses, e.g., masses ofa bond metal such as solder, tin, indium, eutectic composition orcombination thereof or other joining material such as a conductivepaste. In a particular embodiment, the joints between the contacts andthe substrate contacts can include an electrically conductive matrixmaterial such as described in commonly owned U.S. application Ser. Nos.13/155,719 filed Jun. 8, 2011 and 13/158,797 filed Jun. 13, 2011, thedisclosures of which are incorporated by reference herein. In aparticular embodiment, the joints can have a similar structure or beformed in a manner as described therein.

In a particular embodiment, one or more of the microelectronic elementsmay include a semiconductor chip having bond pads disposed in one, two,or more parallel adjacent rows thereon. In a particular embodiment, allof the rows of contacts can be disposed in a central region of thesurface of such chip. Such microelectronic element can have a conductiveredistribution layer formed thereon. For example, such microelectronicelement can include a redistribution layer having metallized vias 92 andtraces 94 coupled to the contacts 20 of the microelectronic element andoverlying the contact-bearing surface of microelectronic element 12, asseen in FIG. 1D, although such microelectronic element omitssemiconductor chip 14 and the conductive structure connected thereto.The redistribution layer may redistribute fine pitch contacts 20 on thesemiconductor chip to redistribution contacts which are suitable forflip-chip bonding to a substrate 1130.

In another variation, first, second, third and fourth microelectronicelements, e.g., semiconductor chips 1112, 1114, 1116, and 1118 havingcontacts, e.g., bond pads, thereon can be arranged as seen in FIG. 13, adielectric layer can be formed on the contact-bearing surfaces of themicroelectronic elements, and a conductive redistribution layer can beformed having metallized vias electrically coupled to the contacts andto terminals at a face of the package. As in the above-describedembodiments, the terminals are available at the face for connection toan external component such as a circuit panel or circuit board, such asthrough joining units, e.g., solder balls among others.

Contacts of microelectronic elements 1112, 1114, 1116, 1118 can bedisposed in one or more rows within a central region of themicroelectronic element, e.g., as described above relative to FIG. 12.Alternatively, the contacts of a microelectronic element can bedistributed across a front face of such microelectronic element. In suchcase, the contacts may be existing conductive pads of themicroelectronic element, such as made during processes used to fabricatea wafer from which the microelectronic element is made. Alternatively,the contacts can be formed in electrical communication with originallyfabricated contacts. Another possibility is for the contacts to beredistribution contacts which are also formed in electricalcommunication with originally fabricated contacts, of which at leastsome are displaced in one or more lateral directions along a surface ofthe microelectronic element from the originally fabricated contacts. Inyet another variation of the embodiment shown in FIG. 13, the contactsof a microelectronic element can be peripheral contacts disposedadjacent one or more of the edges of such microelectronic element.

FIG. 14 further illustrates that the above-described principles ofproviding a central region 1260 of the face of the packaging structurein which shared terminals can be disposed can be applied to packageshaving three microelectronic elements. A shared terminal, or one of many“first terminals” can be disposed within the central region, wherein agroup of electrical connection can electrically couple a first terminalto contacts on each of the first, second and third microelectronicelements 1112, 1114, and 1116. The packaging structure can be asdescribed in any of the embodiments described above.

FIG. 15 illustrates another embodiment in which three microelectronicelements can be packaged together in one unit. In a particular example,substrate 1130 can have first and second microelectronic elements 1112,1114 each having contacts thereon aligned with an aperture or bondwindow 1122, 1124 extending between first and second surfaces of thesubstrate. As seen in FIG. 15, the apertures can have long dimensions,with lengths which extend along parallel axes 1132, 1134. An axis 1126bisects an area of a contact-bearing of the third microelectronicelement 1116 in a direction orthogonal to opposed edges 1118, 1119 ofthe third microelectronic element. The parallel axes 1132, 1134 and axis1126, or the apertures 1122, 1124 and axis 1126 may at least partlybound the central region 1140.

In the embodiment depicted in FIG. 15, microelectronic elements 1112,1114 may be configured to predominantly provide memory storage arrayfunction, such as described above. Another microelectronic element 1116may also be configured to predominantly provide memory storage arrayfunction or another function such as logic.

In variations of the above-described embodiments as illustrated in anyof the foregoing figures, one or more microelectronic elements thereincan each be configured to predominantly provide a memory storage arrayfunction, e.g., as flash memory, DRAM or other type of memory. Such“memory” microelectronic element or “memory chip” may have a greaternumber of active circuit elements, e.g., active semiconductor devices,which are configured to provide memory storage array function than anyother function of the microelectronic element. Such one or more memorymicroelectronic elements can be arranged in a package together withanother “logic” microelectronic element or “logic chip” which isconfigured to predominantly provide logic function. Such “logic”microelectronic element or chip may have a greater number of activecircuit elements, e.g., active semiconductor devices, which areconfigured to provide logic function than any other function of themicroelectronic element.

In a particular embodiment, the logic chip can be a programmable orprocessor element such as a microprocessor or other general purposecomputing element. The logic chip can be a microcontroller element,graphics processor, floating point processor, co-processor, digitalsignal processor, etc. In a particular embodiment, the logic chip canpredominantly perform hardware state machine functions, or otherwise behard-coded to serve a particular function or purpose. Alternatively, thelogic chip can be an application specific integrated circuit (“ASIC”) orfield programmable gate array (“FPGA”) chip. In such variation, thepackage then may be a “system in a package” (“SIP”).

In another variation, a microelectronic element in the package can haveboth logic and memory function embedded therein, such as a programmableprocessor having one or more associated memory storage arrays embeddedtherewith in the same microelectronic element. Such microelectronicelement is sometimes referred to as a “system-on-a-chip” (“SOC”), inthat logic such as a processor is embedded together with other circuitrysuch as a memory storage array or circuitry for performing some otherfunction, which may be a specialized function.

The structures discussed above can be utilized in construction ofdiverse electronic systems. For example, as shown in FIG. 16 a system1200 in accordance with a further embodiment of the invention includes amicroelectronic package or structure 1206 as described above inconjunction with other electronic components 1208 and 1210. In theexample depicted, component 1208 can be a semiconductor chip ormicroelectronic package whereas component 1210 is a display screen, butany other components can be used. Of course, although only twoadditional components are depicted in FIG. 16 for clarity ofillustration, the system may include any number of such components. Thestructure 1206 as described above may be, for example, a microelectronicpackage as discussed above in connection with any of the above-describedembodiments. In a further variant, more than one package may beprovided, and any number of such packages can be used. Package 1206 andcomponents 1208 and 1210 are mounted in a common housing 1201,schematically depicted in broken lines, and are electricallyinterconnected with one another as necessary to form the desiredcircuit. In the exemplary system shown, the system includes a circuitpanel 1202 such as a flexible printed circuit panel or circuit board,and the circuit panel includes numerous conductors 1204, of which onlyone is depicted in FIG. 16, interconnecting the components with oneanother. However, this is merely exemplary; any suitable structure formaking electrical connections can be used. The housing 1201 is depictedas a portable housing of the type usable, for example, in a cellulartelephone or personal digital assistant, and screen 1210 is exposed atthe surface of the housing. Where structure 1206 includes alight-sensitive element such as an imaging chip, a lens 1211 or otheroptical device also may be provided for routing light to the structure.Again, the simplified system shown in FIG. 16 is merely exemplary; othersystems, including systems commonly regarded as fixed structures, suchas desktop computers, routers and the like can be made using thestructures discussed above.

Principles of the invention as described relative to any or all of thefigures herein can be applied to the fabrication, i.e., a method ofmaking a microelectronic package. Thus, a method of making amicroelectronic package according to an embodiment of the invention caninclude forming electrical connections coupling first and secondmicroelectronic elements with packaging structure having a plurality ofterminals disposed at a face thereof such as seen in the figures asdescribed above, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage. The connections can include groups of connections for carryingrespective signals, each group including a first connection extendingfrom a respective terminal of the package to a corresponding contact onthe first microelectronic element and a second connection extending fromthe respective terminal to a corresponding contact on the secondmicroelectronic element, such that a respective signal carried by thefirst and second connections in each group is subject to propagationdelay of the same duration between the respective terminal and each ofthe corresponding contacts coupled thereto.

Methods of fabricating microelectronic packages embodying additionalfeatures or further enhancements as described above can be made inaccordance with the disclosure herein.

Various features of the above-described embodiments of the invention canbe combined in ways other than as specifically described above withoutdeparting from the scope or spirit of the invention. It is intended forthe present disclosure to cover all such combinations and variations ofembodiments of the invention described above.

Moreover, in any of the embodiments described in the foregoing, the oneor more second semiconductor chips can be implemented in one or more ofthe following technologies: DRAM, NAND flash memory, RRAM (“resistiveRAM” or “resistive random access memory”), phase-change memory (“PCM”),magnetoresistive random access memory, e.g. such as may embody tunneljunction devices, spin-torque RAM, or content addressable memory, amongothers.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A microelectronic package, comprising: a substrate having first andsecond oppositely facing surfaces and a plurality of terminals exposedat the first surface, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage; first and second microelectronic elements each having a facefacing the second surface of the substrate; connections electricallycoupling the terminals of the package with the first and secondmicroelectronic elements, the connections including groups ofconnections for carrying respective signals, each group including afirst connection extending from a respective terminal of the package toa corresponding contact on the first microelectronic element and asecond connection extending from the respective terminal to acorresponding contact on the second microelectronic element, the firstand second connections being configured such that a respective signalcarried by the first and second connections in each group is subject topropagation delay of the same duration between the respective terminaland each of the corresponding contacts coupled thereto, wherein thesignals include a plurality of address signals and a sampling signalusable to sample the address signals.
 2. The microelectronic package asclaimed in claim 1, wherein a difference between the total electricallengths of the connections in a respective group of the connections isnot greater than 10 percent, even when distances along straight linesbetween the terminal and the respective contacts coupled by such groupof connections varies by greater than 10%.
 3. A microelectronic packageas claimed in claim 1, wherein the matched delay results at least partlyfrom differences in a spacing of conductors in the electricalconnections relative to other conductive structure of the substrate. 4.A microelectronic assembly including the microelectronic package asclaimed in claim 1, further comprising a circuit panel having circuitcontacts, wherein the terminals of the package are electricallyconnected to the circuit contacts.
 5. The microelectronic package asclaimed in claim 1, wherein at least one of the signals is a clocksignal or a command signal.
 6. (canceled)
 7. The microelectronic packageas claimed in claim 1, wherein the signals further include a commandstrobe signal.
 8. The microelectronic package as claimed in claim 1,wherein the same duration of the propagation delay of the respectivesignal on the first and second connections within each group is within atolerance of ten percent of the cycle time of that signal.
 9. Themicroelectronic package as claimed in claim 1, further comprising athird microelectronic element affixed with the substrate, wherein atleast one of the groups of connections includes a third connectionelectrically coupling the respective terminal to a corresponding contactof the third microelectronic element for carrying the respective signalthereto, wherein the signal carried by the first, second and thirdconnections is subject to propagation delay of the same duration betweenthe respective terminal and each of the corresponding contacts coupledthereto.
 10. The microelectronic package as claimed in claim 9, furthercomprising a fourth microelectronic element affixed with the substrate,wherein at least one of the groups of connections includes a fourthconnection electrically coupling the respective terminal to acorresponding contact of the fourth microelectronic element for carryingthe respective signal thereto, wherein the signal carried by the first,second, third and fourth connections is subject to propagation delay ofthe same duration between the respective terminal and each of thecorresponding contacts coupled thereto.
 11. A microelectronic package,comprising: a substrate having first and second oppositely facingsurfaces and a plurality of terminals exposed at the first surface, theterminals being configured for connecting the microelectronic package toat least one component external to the package; first and secondmicroelectronic elements each having a face facing the second surface ofthe substrate; connections electrically coupling the terminals of thepackage with the first and second microelectronic elements, theconnections including groups of connections for carrying respectivesignals, each group including a first connection extending from arespective terminal of the package to a corresponding contact on thefirst microelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element, the first and second connections beingconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto, wherein the substrate has edges bounding thefirst surface, the first surface having a central region occupying acentral portion thereof, and a second region occupying a portion of thefirst surface between the central portion and at least one of the edges,the terminals including first terminals exposed at the central regionand second terminals exposed at the second region, wherein the groups ofconnections couple the first terminals with the corresponding contacts,wherein the microelectronic package includes further connectionselectrically coupling the second terminals with contacts of themicroelectronic elements.
 12. The microelectronic package as claimed inclaim 11, wherein the substrate has at least first and second aperturesextending between the first and second surfaces, the apertures havinglong dimensions with lengths extending along axes parallel to oneanother, wherein the central region is bounded at least partly by thefirst and second apertures, and the connections include leads havingportions aligned with at least one of the first or second apertures. 13.The microelectronic package as claimed in claim 12, further comprisingthird and fourth microelectronic elements each affixed with thesubstrate, wherein at least one of the groups of connections includesthird and fourth connections electrically coupling the respectiveterminal to corresponding contacts of the third and fourthmicroelectronic elements for carrying the respective signal thereto,wherein the signal carried by the first, second, third and fourthconnections is subject to propagation delay of the same duration betweenthe respective terminal and each of the corresponding contacts coupledthereto, wherein the parallel axes are first parallel axes, and thesubstrate further includes third and fourth apertures extending betweenthe first and second surfaces, the third and fourth apertures havinglong dimensions with lengths extending along second axes parallel to oneanother, the second parallel axes being transverse to the first parallelaxes, wherein the central region is bounded at least partly by the thirdand fourth apertures, and the connections include leads having portionsaligned with at least one of the third or fourth apertures.
 14. Themicroelectronic package as claimed in claim 13, wherein the leads whichhave portions aligned with at least one of the apertures include wirebonds.
 15. The microelectronic package as claimed in claim 14, whereineach of the first, second, third and fourth microelectronic elements isconfigured to provide predominantly a memory storage function.
 16. Themicroelectronic package as claimed in claim 11, further comprising thirdand fourth microelectronic elements each affixed with the substrate,wherein at least one of the groups of connections includes third andfourth connections electrically coupling the respective terminal tocorresponding contacts of the third and fourth microelectronic elementsfor carrying the respective signal thereto, wherein the signal carriedby the first, second, third and fourth connections is subject topropagation delay of the same duration between the respective terminaland each of the corresponding contacts coupled thereto, wherein thecentral region of the first surface is bounded by first parallel axesand second parallel axes transverse to the first parallel axes, eachfirst axis bisecting an area of one of the first and secondmicroelectronic elements, respectively, and extending in a directionparallel to first and second opposed edges of each of the first andsecond microelectronic elements, and each second axis bisecting an areaof one of the third and fourth microelectronic elements, respectively,and extending in a direction parallel to first and second opposed edgesof each of the third and fourth microelectronic elements.
 17. Themicroelectronic package as claimed in claim 16, wherein the substratehas contacts exposed at the second surface facing the microelectronicelements, the contacts of the microelectronic elements facing thesubstrate contacts and joined thereto.
 18. The microelectronic packageas claimed in claim 16, wherein each of the first parallel axesintersects exactly one of the third or fourth microelectronic elements,and each of the second parallel axes intersects exactly one of the firstor second microelectronic elements.
 19. A microelectronic assemblyincluding a microelectronic package as claimed in claim 1, furthercomprising a circuit panel having panel contacts adjacent andelectrically connected to the terminals, the circuit panel havingconductive elements thereon configured to provide delay matching, suchthat signals carried by each group of connections to the microelectronicelements are subject to delay of the same duration through the packagingstructure and the circuit panel.
 20. A microelectronic package,comprising: packaging structure having a plurality of terminals disposedat a face thereof, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage; first and second microelectronic elements affixed with thepackaging structure; connections electrically coupling the terminals ofthe package with the first and second microelectronic elements, theconnections including groups of connections for carrying respectivesignals, each group including a first connection extending from arespective terminal of the package to a corresponding contact on thefirst microelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element, the first and second connections beingconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto, wherein the first and second microelectronicelements are spaced apart from one another in a direction parallel tothe face of the packaging structure.
 21. A microelectronic package,comprising: a substrate having first and second oppositely facingsurfaces and a plurality of terminals exposed at the first surface, theterminals being configured for connecting the microelectronic package toat least one component external to the package; first and secondmicroelectronic elements each having a face facing the second surface ofthe substrate; connections electrically coupling the terminals of thepackage with the first and second microelectronic elements, theconnections including groups of connections for carrying respectivesignals, each group including a first connection extending from arespective terminal of the package to a corresponding contact on thefirst microelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element, the first and second connections beingconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto, wherein the substrate has at least oneaperture extending through the substrate between the first and secondsurfaces, and the second microelectronic element partially overlies thefirst microelectronic element such that contacts of the secondmicroelectronic element are exposed at the face of the secondmicroelectronic element and disposed beyond an edge of the firstmicroelectronic element, wherein the connections to the correspondingcontacts of the second microelectronic element include leads havingportions aligned with the at least one aperture.
 22. The microelectronicpackage as claimed in claim 21, wherein the leads include wire bondsextending through the at least one aperture.
 23. The microelectronicpackage as claimed in claim 21, wherein the at least one apertureincludes first and second bond windows, the connections including firstleads coupled to contacts exposed at the face of the firstmicroelectronic element, the first leads having portions aligned withthe first bond window, and second leads coupled to the secondmicroelectronic element having portions aligned with the second bondwindow.
 24. The microelectronic package as claimed in claim 23, whereinat least some of the terminals with which the first and second leads arecoupled are exposed at the first surface between the first and secondbond windows.
 25. A microelectronic package, comprising: a substratehaving first and second oppositely facing surfaces and a plurality ofterminals exposed at the first surface, the terminals being configuredfor connecting the microelectronic package to at least one componentexternal to the package; first and second microelectronic elements eachhaving a face facing the second surface of the substrate; connectionselectrically coupling the terminals of the package with the first andsecond microelectronic elements, the connections including groups ofconnections for carrying respective signals, each group including afirst connection extending from a respective terminal of the package toa corresponding contact on the first microelectronic element and asecond connection extending from the respective terminal to acorresponding contact on the second microelectronic element, the firstand second connections being configured such that a respective signalcarried by the first and second connections in each group is subject topropagation delay of the same duration between the respective terminaland each of the corresponding contacts coupled thereto, wherein thefirst microelectronic element has contacts at a front face thereof and arear face opposed to the front face, wherein the face of the firstmicroelectronic element is the rear face thereof and is mounted to thesecond surface of the substrate, wherein the leads include wire bondsconnected between the contacts and contacts exposed at the secondsurface of the substrate.
 26. A microelectronic package, comprising: asubstrate having first and second oppositely facing surfaces and aplurality of terminals exposed at the first surface, the terminals beingconfigured for connecting the microelectronic package to at least onecomponent external to the package; first and second microelectronicelements each having a face facing the second surface of the substrate;connections electrically coupling the terminals of the package with thefirst and second microelectronic elements, the connections includinggroups of connections for carrying respective signals, each groupincluding a first connection extending from a respective terminal of thepackage to a corresponding contact on the first microelectronic elementand a second connection extending from the respective terminal to acorresponding contact on the second microelectronic element, the firstand second connections being configured such that a respective signalcarried by the first and second connections in each group is subject topropagation delay of the same duration between the respective terminaland each of the corresponding contacts coupled thereto, wherein at leastone of the first or second microelectronic elements includes a memorystorage array and at least one of the first or second microelectronicelements includes a microcontroller.
 27. A microelectronic package,comprising: packaging structure having a plurality of terminals disposedat a face thereof, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage; first and second microelectronic elements affixed with thepackaging structure; connections electrically coupling the terminals ofthe package with the first and second microelectronic elements, theconnections including groups of connections for carrying respectivesignals, each group including a first connection extending from arespective terminal of the package to a corresponding contact on thefirst microelectronic element and a second connection extending from therespective terminal to a corresponding contact on the secondmicroelectronic element, the first and second connections beingconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto, wherein the packaging structure includes adielectric layer formed on the contact-bearing surfaces of the first andsecond microelectronic elements, traces extending in a directionparallel to the dielectric layer, and metalized vias extending at leastpartly through a thickness of the dielectric layer and electricallycoupled with the contacts of the first and second microelectronicelements, wherein the terminals are exposed at a surface of thedielectric layer and electrically connected to the contacts by thetraces and the vias.
 28. (canceled)
 29. A method of making amicroelectronic package, comprising: forming electrical connectionscoupling first and second microelectronic elements with a plurality ofterminals exposed at a first surface of a substrate having first andsecond oppositely facing surfaces, wherein the first and secondmicroelectronic elements have faces facing the second surface of thesubstrate, the terminals being configured for connecting themicroelectronic package to at least one component external to thepackage, the connections including groups of connections for carryingrespective signals, each group including a first connection extendingfrom a respective terminal of the package to a corresponding contact onthe first microelectronic element and a second connection extending fromthe respective terminal to a corresponding contact on the secondmicroelectronic element, the first and second connections beingconfigured such that a respective signal carried by the first and secondconnections in each group is subject to propagation delay of the sameduration between the respective terminal and each of the correspondingcontacts coupled thereto, wherein the substrate has edges bounding thefirst surface, the first surface having a central region occupying acentral portion thereof, and a second region occupying a portion of thefirst surface between the central portion and at least one of the edges,the terminals including first terminals exposed at the central regionand second terminals exposed at the second region, wherein the groups ofconnections couple the first terminals with the corresponding contacts,and wherein the microelectronic package includes further connectionselectrically coupling the second terminals with contacts of themicroelectronic elements.
 30. A method of making a microelectronicpackage, comprising: forming electrical connections coupling first andsecond microelectronic elements with a plurality of terminals disposedat a first surface of a substrate having first and second oppositelyfacing surfaces, wherein the first and second microelectronic elementshave faces facing the second surface of the substrate, the terminalsbeing configured for connecting the microelectronic package to at leastone component external to the package, the connections including groupsof connections for carrying respective signals, each group including afirst connection extending from a respective terminal of the package toa corresponding contact on the first microelectronic element and asecond connection extending from the respective terminal to acorresponding contact on the second microelectronic element, the firstand second connections being configured such that a respective signalcarried by the first and second connections in each group is subject topropagation delay of the same duration between the respective terminaland each of the corresponding contacts coupled thereto, wherein thesubstrate has at least one aperture extending through the substratebetween the first and second surfaces, and the second microelectronicelement partially overlies the first microelectronic element such thatcontacts of the second microelectronic element exposed at the face ofthe second microelectronic element are disposed beyond an edge of thefirst microelectronic element, wherein the connections to thecorresponding contacts of the second microelectronic element includeleads having portions aligned with the at least one aperture.
 31. Themicroelectronic package as claimed in claim 11, wherein at least some ofthe first terminals overlie at least one of the faces of the first orsecond microelectronic elements.
 32. The microelectronic package asclaimed in claim 21, wherein the face of the second microelectronicelement faces the first microelectronic element and the substrate, theface of the second microelectronic element having first and secondperipheral regions adjacent to first and second opposed peripheral edgesof the second microelectronic element, respectively and the contacts ofthe second microelectronic element being disposed in a central region ofthe face of the second microelectronic element between the first andsecond peripheral regions, the central region and the first and secondperipheral regions having equal width in a direction between the firstand second peripheral edges, such that the central region occupies amiddle third of a shortest distance between the first and secondperipheral edges.
 33. The microelectronic package as claimed in claim32, wherein the face of the first microelectronic element facing thesubstrate has first and second peripheral regions adjacent to first andsecond opposed peripheral edges of the first microelectronic element,respectively, and the contacts of the first microelectronic element aredisposed in a central region of the face of the first microelectronicelement between the first and second peripheral regions of the firstmicroelectronic element, the central region and the first and secondperipheral regions of the first microelectronic element having equalwidth in a direction between the first and second peripheral edges ofthe first microelectronic element, such that the central region of thefirst microelectronic element occupies a middle third of a shortestdistance between the first and second peripheral edges of the firstmicroelectronic element.
 34. The microelectronic package as claimed inclaim 23, wherein the first leads have no portions aligned with thesecond bond window, and the second leads have no portions aligned withthe first bond window.
 35. The microelectronic package as claimed inclaim 20, wherein the packaging structure includes a substrate havingfirst and second oppositely facing surfaces, wherein the terminals areexposed at the first surface and the first and second microelectronicelements have faces facing the second surface.
 36. The microelectronicpackage as claimed in claim 35, wherein at least some of the terminalsunderlie at least one of the microelectronic elements.
 37. Themicroelectronic package as claimed in claim 35, wherein at least some ofthe terminals underlie at least one of the microelectronic elements. 38.The microelectronic package as claimed in claim 35, wherein at leastsome of the terminals are exposed at a portion of the first surface ofthe substrate aligned with a spacing between an edge of the firstmicroelectronic element and an adjacent edge of the secondmicroelectronic element.